I like this a lot. Even with clear criterias, I could fill out a form in a negative way. Who's gonna proof that I had done this in a dishonest way? Sure, if I would go so far, I would not be a good sports myself, but I heard from people being stingy about a loss and getting their revenge with that and those stories have been coming from different systems and persons on more than one Occasion.
If you have to vote just for a fun opponent, there is no room to get revenge on, since even if you lost every single match, you at least have to give someone the thumbs up.